Stop device with shape memory actuator

Abstract

A stop device with a shape memory actuator includes two stop elements sliding within a fixed support structure and usually hold in their mutual distant position by cam means pushed through spring means. A shape memory actuator is started through an electric current passage for causing the displacement of the cam means in a position wherein they permit the backward movement of the two stop elements towards a mutual close position.

1. Stop device, comprising:
 a fixed support structure, 
 a pair of stop elements slidably mounted within the support structure and movable among a mutual close position and a mutual distant position, wherein they protrude from the opposite sides of the fixed structure for co-operating with a corresponding stop surface, 
 first spring means tending to return the two stop elements to their mutual close position, 
 cam means for pushing the two stop elements towards their mutual distant position, against the action of said first spring means, 
 second spring means for pushing the two stop elements towards a position wherein they hold the two stop elements in their mutual distant position, and 
 a shape memory actuator for returning said cam means, against the action of said second spring means, towards a position wherein the two stop elements can freely move in their mutual close position, under the action of said first spring means. 
 
   
   
     2. Device according to  claim 1 , wherein the aforesaid cam means consist of one wedge-shaped element having two slanted opposite V-shaped sides co-operating with slanted surfaces facing each other of the two stop elements. 
   
   
     3. Stop device according to  claim 2 , wherein said wedge-shaped element is provided with a portion with a semi-circumferential groove for the engagement of said shape memory wire. 
   
   
     4. Device according to  claim 2 , wherein the slanted opposite sides of the wedge-shaped element are V-shaped in an orthogonal plane with respect to the plane defined by the two parallel branches of the shape memory wire. 
   
   
     5. Stop device according to  claim 1 , wherein said actuator includes at least one or more shape memory wires interposed among the fixed support structure and said cam means, and means for supplying an electric current through the aforesaid shape memory wires, in order to cause the heating and the consequent shortening due to the shape memory effect, thus causing a displacement of the aforesaid cam means towards a position where they allow the backward movement of the two stop elements towards their mutual close position. 
   
   
     6. Device according to  claim 5 , wherein it includes two wires arranged in parallel between a fixed structure and cam means. 
   
   
     7. Device according to  claim 6 , wherein the two wires are defined by two branches of one single wire U-returned around said cam means. 
   
   
     8. Device according to  claim 7 , wherein the aforesaid shape memory wire is obtained by extrusion along with a synthetic material coating. 
   
   
     9. Device according to  claim 8 , wherein the opposite adjacent ends of the shape memory wire are secured to two bushings, both fixed to the end of a metal tube fastened to the support structure. 
   
   
     10. Device according to  claim 9 , wherein within said metal tube a sheath is arranged, which is crossed by the aforesaid shape memory wire with the relative co-extruded coating.